The invention relates to polysiloxanes containing carboxyl groups and intended for imparting water-repellency to substrates, in particular paper, textiles, leather or hides, in particular to leather and hides, and a process for their preparation, a water-repellent system containing this polysiloxane and a process for the production of hydrophobic substrates.
Upper leather, bag leather, apparel leather or automobile and furniture leather can be treated with softening retanning agents and water repellents so that a supple; water-repellent leather (waterproof leather) results, which does not permit penetration of water even under dynamic load. To achieve comfortable wear properties, leathers having high water vapour permeability are required. This is necessary, for example, for shoes or apparel leather.
Silicones containing carboxyl groups are disclosed in DE-A-35 29 869, DE-A-38 00 629 and WO 95/22627. These are silicones which contain carboxyl groups and whose COOH groups are linked to the silicone main chain via an alkylene group. The availability of these compounds on the industrial scale is however limited: the synthesis could be carried out, for example, by a platinum-catalyzed addition reaction of acids having unsaturated terminal groups with silicone oils having SiH functional groups, it being necessary to avoid secondary reactions by using protective groups. Finally, the protective group must also be removed hydrolytically by means of bases or acids. Such processes are also expensive. Furthermore, the stability of such emulsions during storage is still insufficient and the water-repellent effect is unsatisfactory.
DE-A-44 04 890 describes a process for imparting water-repellency to leather with polysiloxanes containing carboxyl groups in an aqueous emulsion in the presence of emulsifiers, which is characterized in that polysiloxanes, carboxyl-functionalized in a comb-like manner are used, in which the carboxyl groups are linked to the polymer main chain via spacer groups in the form of linear or branched C2- to C40-alkylene groups which can be interrupted by specific substituents. In the Examples, water-repellency is imparted to leather with polysiloxanes whose carboxyl groups are linked to the polysiloxane main chain via a (CH2)10 spacer. Maeser values of 15000-30000 or 20000 to  greater than 100000 flexes were obtained by mineral salt fixation.
DE-C-196 46 916 relates to the use of carboxamido-polysiloxanes which are obtainable by reacting polysiloxanes having amino functional groups with dicarboxylic anhydrides for imparting water-repellency to materials of fibrous structure, in particular to leather and hides. The carboxyamido-polysiloxanes have a carboxyl group content of from 0.02 to 1.0 mmol/g and a molar mass Mn in the range from 2000 to 60000 g/mol. When these compounds are used, the leather treatment can be carried out in an aqueous liquor. Moreover, aftertreatment with metal salts and the use of emulsifiers and solvents is said to be unnecessary. The compounds mentioned in DE-C-196 46 916 can be prepared according to EP-A-95 676. However, as is evident from the Application Examples of DE 196 46 916, they do not reach the water-repellency values required for waterproof leather. As a rule, more than 50000 flexes are required in the Maeser test (based on ASTM D 2099-70). This is the number of flexes which the leather must withstand in a water bath under mechanical compression without water penetration. The leathers stated in DE-C- 196 46 916 become water-permeable only after a number of compressions 50% higher than the control (14600 compressions) (page 14, lines 45 to 47). Consequently, in spite of this progress, the achievable water-repellency effect is still insufficient. In the description, reference is made to the customary fixation with formic acid. The effect of imparting water-repellency can be enhanced by an aftertreatment with a divalent, trivalent or tetravalent metal salt customary in tanning, in particular with a basic chromium sulphate, with aluminium sulphate, zirconium sulphate, titanium sulphate, calcium chloride or magnesium sulphate (page 9, lines 25 to 27). In the Examples, use is also made of fixation with a chromium salt. Nevertheless, the Maeser values are still too low for many requirements. Conversely, however, this means that the fixation in the absence of metal salts is still in need of improvement.
However, with the use of carboxamido-polysiloxanes, polysiloxanes containing carboxyl groups and in particular polysiloxanes which contain free amino groups, further disadvantages still occur. The leathers dyed with customary dyes have a nonuniform colour intensity which may manifest itself in particular in the leather having two different sides. This means a colour difference between the grain side and flesh side of the leather, the flesh side appearing to have a substantially more intense colour than the grain side. The handle of the leather, too, is often silky, undesirably silicone-like or greasy when the known silicones are used.
DE-A-196 29 986 relates to a process for imparting water-repellency to leathers which have been tanned, in the absence of vegetable, synthetic and mineral tanning agents, only with polymer tanning agents and optionally, for pretanning, with aldehydes or reactive carbonyl compounds, in which polysiloxanes according to WO 95/22627 (polysiloxanes carboxyl-functionalized in a comb-like manner) are used as water repellents. For these products, too, fixation with zirconium salts is described, in order to achieve sufficient water-repellency effects.
DE-A-196 39 782 describes water-based organopolysiloxane-containing compositions which, when diluted with water, liberate essentially no alcohols and contain glycidyl ether alkyl and/or (meth)acryloyloxyalkyl groups as functional groups, each silicon in the organopolysiloxane carrying a functional group. In addition, aminoalkyl radicals are also claimed as a further functional group. The products are prepared by cohydrolysis of water-soluble organosilanes and are recommended, inter alia, for imparting water repellency to textile, leather and cellulose and starch products. Carboxyl groups are not mentioned as substituents.
DE-A-196 51 287 Al relates to ionic organosilicon compounds and their preparation and use. The claimed compounds are preferably obtained by an addition reaction of the double bond of functional acrylates or acrylamides with aminopolysiloxanes. The claimed ionic organosilicon compounds complex with transition metals and can thus bind permanently in the leather treatment (chrome-tanned leathers) and lead to a permanent hydrophilic treatment with the desired soft handle. In textile treatment, too, they have the advantage of leading to a soft handle with good body in addition to very good hydrophilic properties and very good antistatic properties (page 20, lines 21 to 27). These are in principle polysiloxanes having betaine character. Such products are however less suitable for imparting to leather water-repellency which must also withstand water penetration under dynamic loads, since the incorporated betaine groups do not lose their hydrophilic character (which however is desirable according to the statements in DE 196 51 287) and thus adversely affect the water-repellency effect.
DE-A-197 07 970 relates to polyorganosiloxanes having polycarboxylic acid functional groups. They are preferably prepared by reacting polysiloxanes having amino functional groups with polycarboxylic anhydrides, tricarboxylic anhydrides and tetracarboxylic anhydrides being used. Thus, at least two carboxyl groups are bonded to each amino group of the silicon via an amido group. This particular arrangement of at least two carboxyl groups per radical having a polycarboxylic acid function leads to high affinity of the polyorganosiloxanes having polycarboxylic acid functional groups to cationic substrates, in particular metal ions, owing to the chelate effect. Consequently, they are particularly suitable for the treatment of tanned leather (page 3, lines 2 to 5). However, the Examples propose a procedure in organic solvents which is no longer relevant in practice in the leather industry: thus, the silicones are present as solutions in petroleum ether or methyl isobutyl ketone (MiBK). The stated water-repellency values (static water absorption and Bally penetrometer) are as a rule insufficient.
DE-A-43 30 378 discloses anionic urethanes containing cyanamide groups and having relatively long hydrocarbon radicals, which are suitable as retanning agents for leather and textiles and as emulsifiers. As emulsifiers, the claimed compounds have the advantage that, after use, they dimerize or oligomerize and thereby lose their ionic character and hence their hydrophilic properties. However, the products are likewise inadequate in their water-repellency effect if they are used alone.
The publication by H. Birkhofer, Das Leder [Leather] 43, pages 71-75 (1992) discloses reactive water repellents based on polymers having reactive groups.
Polysiloxanes containing alkylsulphosuccinates and sulphosuccinic acid groups require no fixation with mineral salts: M. Kaussen, H. Lohmann, H. Kilian, Das Leder [Leather] 43 (9), pages 223-227 (1992) and DE 42 14 150. However, the water-repellency effect of such products is likewise still in need of improvement since sulpho groups in general impart excessively high hydrophilicity to the treated leather.
In EP-A-579 267 and EP-A-372 746, amphiphilic copolymer dispersions which are prepared by copolymerization of hydrophilic monomers, preferably acrylic acid, and hydrophobic monomers, preferably long-chain alkyl methacrylate, are used. Leathers which are washable or are suitable for dry cleaning are obtained. The products achieve their maximum effect only through retanning with mineral tanning agents, in particular with chromium salts.
EP-A-891 430 describes the use of copolymers of dicarboxylic acid (anhydrides), (maleic anhydride) and lower olefins (isobutene) and hydrophobic comonomers (C20-C24-olefins) in retanning/fatliquoring of leather/imparting water repellency to leather, also in combination with paraffin water repellents or silicone water repellents. These combinations, too, display their full water repellency effect only after fixation with mineral salts, in particular with chromium salts.
EP-A-757 108 discloses a process for the preparation of water-repellent leathers with silicone oils which are dispersed in a copolymer comprising an unsaturated water-soluble acidic or basic monomer and a hydrophobic comonomer. Very good water-repellency effects can be achieved with the products used, only in combination with chromium salt fixation.
Thus, numerous water repellents have already been proposed. The known products meet the various, high requirements for the water repellency of the finished leather, the requirements with respect to the handle properties, the tensile strength, the uniformity of colour, the finishability and the water vapour permeabilityxe2x80x94generally a combination of several of these properties are requiredxe2x80x94only to an insufficient extent. In addition, they must be fixed with mineral salts in order to achieve the optimum with regard to water repellency. Water repellents fixed with formic acid give leathers which already have a certain hydrophobic character but which are not optimally suitable for use as upper leather: hydrophobic leathers should have a reduced static water absorption and a water-repellent effect and additionally be waterproof under high dynamic load, have a soft handle and moreover be permeable to water vapour in order to ensure a high degree of comfort when worn. However, they may not change the mechanical strength of the leather article even in the case of soft leathers, which is particularly important for upper leather. In addition, the leather surface may not stick or have the typical silicone handle. Moreover, the body of the leather should be advantageously affected. Further requirements consist in the lightfastness and heat stability of the leather. Permanence of the water repellency is also desired. Wet fastness and colour fastness are particularly important for apparel leather. From the point of view of the application, it is also necessary to fulfil requirements which permit convenient use by the customer: the products should have low viscosity and should be dilutable with water. In addition, they should have the required shelf-life. Silicone products in particular are generally critical in this respect since they are either too coarse-particled and then tend to phase separation or contain additional emulsifiers which adversely affect the water repellency and have a wetting effect. The leathers treated with water repellents furthermore may not exhibit undesired loose grain. The finishability of hydrophobic leathers, too, is a major problem since the adhesion of aqueous coatings to the hydrophobic substrate is unsatisfactory or, in the case of too superficial a seat of the silicone, an aqueous coating material for leather finishing would be repelled directly during the attempt at application.
Furthermore, there is an application problem in converting the hydrophobic active ingredient into a stable and finely divided emulsion in order to achieve rapid and uniform distribution of the active ingredient in the drum liquor during use in the tannery. The emulsifiers used to date remain in the leather and counteract the water-repellency effect and should therefore be avoided in water repellents. It is also necessary to achieve complete exhaustion of the liquor. This is because product which is not applied incurs high costs for the leather manufacturer and pollutes the environment.
The water repellents used according to the prior art thus furthermore require some improvements. Products which preferably exhibit the same efficiency exclusively with formic acid fixation as with the fixation customary to date using chromium salts or other mineral salts and which meet the above-mentioned requirements are desired. It is advantageous for the user to reduce the time spent by shortening the individual steps in leather manufacture or by combining specific treatment steps. In this context, liquor change and washing processes must be minimized in practice. The tanner furthermore expects products which are readily compatible with the customary auxiliaries which are used in retanning, dyeing and fatliquoring.
The object of the present invention is the provision of an aqueous water-repellent system for leather or hides which, with a simple acid fixation, achieves waterproof properties which are just as good as with classical mineral salt fixation and moreover meets requirements with respect to softness, uniformity of colour, finishability, and water vapour permeability of the leathers produced therewith.
It is also the object of the invention to provide a water-repellent system which contains additional emulsifiers, which do not impair the hydrophobic properties and, on drying, lose their effectiveness as an emulsifier (self-inhibiting emulsifiers), and which is permanently fixed in the leather.
It has surprisingly been found that the disadvantages, described above, of the water repellents according to the prior art are avoided if a water-repellent system containing
a) a polysiloxane containing carboxyl groups, which is characterized in that the polysiloxane chain contains at least one structural unit of the formula (1)
[ARaSiO(3xe2x88x92a)/2]kxe2x80x83xe2x80x83(1)
xe2x80x83and/or at least one structural unit of the formula (2)
[RcSiO(4xe2x88x92c)/2]nxe2x80x83xe2x80x83(2)
xe2x80x83and optionally at least one terminal group selected from the formulae
R3SiO1/2xe2x80x83xe2x80x83(3)
and
AR2SiO1/2xe2x80x83xe2x80x83(3a),
A representing a radical containing carboxyl groups and of the formula 
xe2x80x83in which
R1, R2 and R3, independently of one another, represent hydrogen or a monovalent C2-C60-hydrocarbon radical which optionally contains one or more non-neighbouring ether, imino, amido, urea, urethane, ester or carboxyl groups and which is optionally substituted by one or 2 carboxyl groups xe2x80x94COOM and/or 1 or 2 hydroxyl groups, and
xe2x80x83the radical A being substituted at least by one group COOM,
M representing hydrogen or Na+, K+, Li+, NH4+, 
R4, R5 and R6, independently of one another, representing C1-C18-alkyl, in particular C1-C4-alkyl or substituted C1-C18-alkyl, in particular hydroxyalkyl or aralkyl, in particular benzyl,
and R1 to R3, independently of one another, being linked to the nitrogen atom via a single bond or a group xe2x80x94COOxe2x80x94, xe2x80x94COxe2x80x94 or xe2x80x94CONHxe2x80x94, and
R1 and R2 not simultaneously representing H and also not simultaneously being linked to the nitrogen atom via a carbonyl group,
D and E, independently of one another, represent a divalent C2-C20-hydrocarbon radical which may be substituted by hydroxyl or interrupted by non-neighbouring O atoms,
q represents 0 to 3,
R represents a C1- to C12-alkyl radical or a phenyl radical,
a represents 0 or 1,
k represents 0 to 50,
c represents 1 or 2 and
n represents 10 to 1000,
xe2x80x83with the proviso that at least one terminal group of the formula (3a) is present where the polysiloxane chain contains only structural units of the formula (2), and
b) at least one component from the group B1 to B4,
B1 being an anionic copolymer,
B2 being polyaspartic acid or a derivative thereof,
B3 being a paraffin and
B4 being an isocyanate adduct,
xe2x80x83is used.
Preferred polysiloxanes a) containing carboxyl groups have, for example, the following structures: 
Linear polysiloxanes a) are particularly preferred.
In the context of this application, xe2x80x9csystemxe2x80x9d in the term xe2x80x9cwater-repellent systemxe2x80x9d is understood as meaning that the components a) and b) of the system are used as individual components, for example in the form of their aqueous solutions or dispersions, or are present in any desired combination with one another. It is preferable to use the components of the system as individual components simultaneously or in succession. Preferably, the polysiloxane a) is used as the last component after one or more components B1 to B4. Furthermore, it is preferable to use polysiloxane a) and component B4 after one or more components B1 to B3.
Preferred polysiloxanes a) containing carboxyl groups are those in which, in the meaning of the substituent A in the above-mentioned formula (1), the radicals R1 to R3, independently of one another, represent a radical of the formula (1a) 
in which
G1 and G2, independently of one another, represent H or CH3,
X1 represents a divalent hydrocarbon radical having 2 to 30 carbon atoms,
W represents H or the group 
Z1 representing a divalent hydrocarbon radical having 1 to 20 carbon atoms and
M having the above-mentioned meaning,
p represents 0 to 5,
f represents 0 or 1,
g represents 0 to 3,
or of the formula (1b) 
in which
G1, G2, X1, W, p, f, g and M have the above-mentioned meaning and
X2 represents a divalent hydrocarbon radical having 2 to 20 carbon atoms,
Z2 represents a divalent hydrocarbon radical having 1 to 20 carbon atoms which may optionally be substituted by a further group xe2x80x94COOM, xe2x80x94NH2 or xe2x80x94OH, M having the above-mentioned meaning, and
Y represents xe2x80x94Oxe2x80x94, xe2x80x94NHxe2x80x94 or xe2x80x94N(C1-4-alkyl)- ,
or of the formula (1c)
xe2x80x94Z3xe2x80x94COOMxe2x80x83xe2x80x83(1c)
in which
Z3 represents an alkylene radical having 1 to 10 carbon atoms which may optionally be substituted by a further group xe2x80x94COOM, and
M has the above-mentioned meaning.
Radicals R1 to R3 of the formulae 
or xe2x80x94Z3xe2x80x94COOM,
G2 representing H or CH3 and
X1, X2, Z1, Z2, Z3, Y, M and p having the above-mentioned meaning,
are particularly preferred.
Suitable radicals X1 are, for example,
xe2x80x94(CH2)5xe2x80x94, xe2x80x94(CH2)4xe2x80x94, xe2x80x94(CH2)3xe2x80x94, xe2x80x94CH2CH2xe2x80x94, 
Suitable radicals X2 are, for example, 
Suitable radicals Z1 are, for example, 
Suitable radicals Z2 are, for example,
xe2x80x94CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, 
xe2x80x94(CH2)10xe2x80x94, xe2x80x94(CH2)3xe2x80x94.
Suitable radicals Z3 are, for example,
xe2x80x94CH2xe2x80x94, xe2x80x94CH2xe2x80x94CH2xe2x80x94, 
Preferred substituents A are 
Polysiloxanes a) according to the invention and to be used are composed of functionalized siloxane units, such as those of the formulae (1) and optionally of the formula (3a), and unfunctionalized siloxane units, such as those of the formula (2) and optionally of the formula (3). Preferably, the polysiloxanes a) contain on statistical average 50 to 1000, particularly preferably 50 to 400, unfunctionalized siloxane units (2) and 1 to 50, particularly preferably 1 to 20, functionalized siloxane units (1), it being possible for the siloxane units to be arranged in any desired sequence within the polymer chain. Preferably, the linear polysiloxanes a) contain 2 terminal groups of the formulae (3) and/or (3a), particularly preferably terminal groups of the formula (3). It is also possible for the polysiloxanes a) to have a cyclic structure known per se, in which case they contain only structural units of the formulae (1) and (2). This is the case if a in formula (1) represents a=1 and c in formula (2) represents c=2. It is furthermore possible for the polysiloxanes a) containing carboxyl groups to have a branched structure. This is the case if a in formula (1) represents a=0 and/or c in formula (2) represents c=1. Depending on the degree of branching, branched polysiloxanes contain a terminal group of the formula (3) or (3a) at the end of each branching siloxane chain. Each chain emanating from the branching point may contain a different number of siloxane units of the formula (1) and/or (2), the sum of these units corresponding to the definition of k and n. A polysiloxane a) may contain different substituents A. It is also possible for polysiloxanes having different radicals A to be mixed in the polysiloxane chains. The polysiloxanes to be used according to the invention preferably contain functionalized siloxane units in the following ratio, based in each case on the totality of all functionalized sitoxane units in the formulae (1) and (3a):
80-100 mol %, preferably 90-100 mol %, of siloxane units functionalized by carboxyl groups (xe2x80x94COOM) and
0-20 mol %, preferably 0-10 mol %, of siloxane units functionalized by hydroxyl groups and/or amino groups (xe2x80x94NHxe2x80x94, xe2x80x94NH2)
0-10 mol %, preferably 0-5 mol %, of siloxane units functionalized by hydroxyl and carboxyl groups (xe2x80x94COOM).
The amino groups are preferably those which result from a reaction which may be incomplete (see process).
Preferred polysiloxanes a) are those which
have an average molar mass of 1000 to 100000 g/mol, particularly preferably 2000 to 50000 g/mol, and/or
have a content of carboxyl groups or of salts thereof of 0.05 to 1.5 mmol of COOM per gram of polysiloxane active ingredient and/or
have a content of hydroxyl groups of 0 to 0.15 mmol of OH per gram of polysiloxane active ingredient.
The invention furthermore relates to novel polysiloxanes which contain carboxyl groups and are characterized in that they contain at least one structural unit of the formula (1d)
[A1RaSiO(3xe2x88x92a)/2]kxe2x80x83xe2x80x83(1d)
and/or at least one structural unit of the above-mentioned formula (2) and optionally at least one terminal group selected from the formulae
R3SiO1/2xe2x80x83xe2x80x83(3)
and
A1R2SiO1/2xe2x80x83xe2x80x83(3d),
A1 representing a radical from the group 
xe2x80x83M, R, a and k having the above-mentioned meaning,
with the proviso that at least one terminal group of the formula (3d) is present where the polysiloxane chain contains only structural units of the formula (2).
The polysiloxanes according to the invention are composed of functionalized siloxane units of the formula (1d) and optionally (3d) and unfunctionalized siloxane units of the formula (2) and optionally of the formula (3). Preferably, the polysiloxanes contain on statistical average 50 to 1000, particularly preferably 50 to 400, unfunctionalized siloxane units and 1 to 50, particularly preferably 1 to 20, functionalized siloxane units. The polysiloxanes according to the invention preferably contain functionalized siloxane units in the following ratio, based in each case on the totality of all functionalized siloxane units in the formulae (1d) and (3d):
80-100 mol %, preferably 80-98 mol %, of siloxane units functionalized by carboxyl groups (xe2x80x94COOM) and
0-20 mol %, preferably 2-20 mol %, of siloxane units functionalized by hydroxyl groups and/or
0-10 mol %, preferably 0-5 mol %, of siloxane units functionalized by hydroxyl groups and carboxyl groups (xe2x80x94COOM).
Suitable polysiloxanes according to the invention are also those which have a hydroxyl group and at least one carboxyl group xe2x80x94COOM on the radicals A1, or those whose radicals A1 have a different content of carboxyl groups and/or hydroxyl groups.
The invention furthermore relates to a process for the preparation of the polysiloxanes according to the invention, which is characterized in that an aminopolysiloxane which contains structural units of the formula (2)
[RcSiO(4xe2x88x92c)/2]nxe2x80x83xe2x80x83(2)
and structural units of the formula (4)
[Axe2x80x2RaSiO(3xe2x88x92a)/2]kxe2x80x83xe2x80x83(4)
and/or optionally terminal groups of the formula
Axe2x80x2R2SiO1/2xe2x80x83xe2x80x83(4a)
and/or optionally terminal groups of the formula (3)
R3SiO1/2xe2x80x83xe2x80x83(3)
in which
R, a, c, k and n have the above-mentioned meaning and
Axe2x80x2 represents a radical of the formula 
xe2x80x83in which D, E and q have the above-mentioned meaning,
is reacted
optionally after prior reaction with C1-C10-alkylene oxides to give the corresponding hydroxyalkyl-aminopolysiloxanesxe2x80x94with a lactone (6a) 
xe2x80x83or a cyclic carbonate (6b) 
xe2x80x83in which
X1 represents a divalent hydrocarbon radical having 2 to 30 carbon atoms,
xe2x80x83and the resulting hydroxyl-functionalized polysiloxane which contains structural units of the formula (2)
[RcSiO(4xe2x88x922)/2]nxe2x80x83xe2x80x83(2)
and of the formula (5)
[Axe2x80x3RaSiO(3xe2x88x92a)/2]kxe2x80x83xe2x80x83(5)
and/or optionally terminal groups of the formula
xe2x80x83Axe2x80x3R2SiO1/2xe2x80x83xe2x80x83(5a)
and/or optionally of the formula (3)
R3SiO1/2xe2x80x83xe2x80x83(3),
R, a, c, k and n having the above-mentioned meaning and
Axe2x80x3 representing the radical 
q, D and E having the above-mentioned meaning and
R1a, R2a and R3a representing H or the group 
G1, G2, p, f, g and X1 having the above-mentioned meaning,
is reacted with a polycarboxylic acid derivative of the formula
R11OOCxe2x80x94Z1xe2x80x94COOR11
or with a polycarboxylic anhydride of the formula (6c) 
Z1 having the above-mentioned meaning and
R11 representing C1- to C4-alkyl, and the resulting polysiloxane, which contains structural units containing carboxyl groups (having functional groups COOH), is converted with bases into the salt form (COOxe2x8ax96M⊕), M having the above-mentioned meaning.
The reaction of amines with lactones or carbonates is known per se, as is the reaction of hydroxy compounds with anhydrides to give carboxyl-containing compounds (monoester formulation).
The aminopolysiloxanes used are commercially available or are obtainable, for example, by base-catalyzed reaction of polydimethylsiloxanes with aminoalkyl-dialkoxy-alkyl-silanes (equilibrium reactions) with removal of the resulting alcohol by distillation.
The invention furthermore relates to a process for the preparation of the polysiloxanes according to the invention which are substituted by radicals A1 which are interrupted by urethane or urea groups, which is characterized in that an aminopolysiloxane which contains structural units of the above-mentioned formulae (2), (4) and/or optionally (4a) and/or optionally (3) or a polysiloxane prepared therefrom, having hydroxyl functional groups and containing structural units of the above-mentioned formula (5) and optionally of the above-mentioned formula (5a) and/or (3) is reacted with a polyisocyanate of the formula (7)
X2(NCO)txe2x80x83xe2x80x83(7),
X2 representing a t-valent radical having 2 to 30 carbon atoms and
t representing 2 or 3, preferably 2,
and the NCO-functionalized polysiloxane obtained is reacted with a hydroxycarboxylic or aminocarboxylic acid of the formula (8) or (8a), respectively,
H2Nxe2x80x94Z2xe2x80x94COOHxe2x80x83xe2x80x83(8)
HOxe2x80x94Z2xe2x80x94COOHxe2x80x83xe2x80x83(8a)
Z2 representing a divalent C1- to C20-hydrocarbon radical which may be substituted by carboxyl, amino or hydroxyl groups,
the remaining NCO groups being completely reacted,
and the polysiloxane containing carboxyl groups is then neutralized with a base, the carboxyl groups being converted into the salt form xe2x80x94COOxe2x8ax96M⊕.
The polysiloxanes a) to be used according to the invention can be prepared in a manner analogous to that described above.
Preferred raw materials for the preparation of polysiloxanes according to the invention are, as described above, aminopolysiloxanes known per se, which are obtained by reacting unfunctionalized polysiloxanes, such as polydimethyl-polysiloxanes, preferably having a viscosity of 500 to 12500 mPas at 20xc2x0 C., with an aminosilane of the fonnula 
in which
s represents 0 or 1 and E, D, R and q have the above-mentioned meaning, and
R21 represents methyl or ethyl,
preferably with N-(2-aminoethyl)-3-aminopropyldimethoxymethylsilane or N-(2-aminoethyl)-3-aminopropyldiethoxymethylsilane or 3-aminopropyldi(m)ethoxymethylsilane, in the presence of basic catalysts, preferably NaOH, KOH, trialkylammonium hydroxides or strongly basic ion exchangers. Polysiloxanes having a viscosity between 500 and 6000 mPas at 20xc2x0 C. are particularly preferred as raw materials for the preparation of the aminopolysiloxanes.
Preferably, dimethylpolysiloxanes and the corresponding aminosilanes are used in an amount such that polysiloxanes which contain amino groups and whose base N content is 0.1% to 2.0% by weight, preferably 0.2 to 1.0% by weight and particularly preferably 0.25 to 0.8% by weight, are formed. The viscosity of the aminopolysiloxanes at 20xc2x0 C. (D=100 sxe2x88x921) is preferably 50 to 2000 mPas, preferably 50 to 1000, particularly preferably 50 to 500, more preferably 50 to 200, mPas.
The polysiloxanes according to the invention are preferably obtained from the aminopolysiloxanes, optionally after reaction with C2-C8-alkylene oxides, preferably ethylene oxide and/or propylene oxide, by reaction with lactones, preferably xcex3-butyrolactone or caprolactone, and/or by reaction with cyclic carbonates, preferably ethylene carbonate, propylene carbonate or mixtures thereof, and simultaneous or subsequent reaction with dicarboxylic acid derivatives or dicarboxylic anhydrides, preferably maleic anhydride, succinic anhydride, phthalic anhydride, diethyl maleate or tetrahydrophthalic anhydride, and subsequent neutralization with bases of the carboxyl groups present in the product obtained. A reaction with dicarboxylic acid derivatives or anhydrides after the reaction with the lactone or cyclic carbonate is preferred. The subsequent dispersing in water gives the emulsions of the polysiloxanes.
It is also possible to react the hydroxyl groups present in the aminopolysiloxanes derivatized with alkylene oxides and/or lactones or carbonates with polyisocyanates, preferably only a part of the NCO groups reacting and no crosslinked products forming. The remaining NCO groups are preferably converted by reaction with hydroxycarboxylic or aminocarboxylic acids, converted into the salt with a base and correspondingly dispersed in water. In the last-mentioned case, radicals R1 to R3 containing urethane groups form.
Preferably 0.4 to 1.05 equivalents of lactone or cyclic carbonate are used for acylation per equivalent of basic amino group which is contained in the polysiloxane containing amino groups. The molar ratio of polycarboxylic anhydride (or ester) to base N is likewise 0.8:1 to 1.05:1. Preferably, 0.5 to 1.0 equivalent of lactone or cyclic carbonate is used per equivalent of nitrogen and then 0.9 to 1.05 equivalents of polycarboxylic anhydride are used. The reaction is preferably carried out without a solvent in the temperature range between 10xc2x0 C. and 150xc2x0 C., preferably between 30 and 120xc2x0 C. In the case of viscous products, a solvent which is inert to anhydrides or lactones can be added to improve the handling or the solubility. The following may be mentioned by way of example: tetrahydrofuran, acetone, NMP, pyrrolidone, diethylene glycol dimethyl ether, DMSO, methyl ethyl ketone, ethyl acetate, chloroform and toluene. A reaction in acetone or ethyl acetate or without a solvent is preferred.
It is also preferable to distil off the solvent after the reaction with the lactone, before the further reaction with the anhydride is carried out.
It is furthermore preferable to use 0.4 to 1.05 equivalents of alkylene oxide and/or 0.4 to 1.05 equivalents of cyclic carbonate or lactone per equivalent of basic amino group which is contained in the aminopolysiloxane and to react the resulting hydroxypolysiloxanes with the dicarboxylic anhydride in the molar OH:anhydride ratio=1:1. Optionally, amino groups of the aminopolysiloxane raw material used which are still present are preferably reacted quantitatively with the dicarboxylic acid anhydride, simultaneously with the hydroxyl groups.
After the end of the reaction, the carboxyl groups present in the product are neutralized. 0.8 to 1.1 mol of a base are used per carboxyl equivalent. The reaction is carried out at 10xc2x0 C. to 100xc2x0 C., preferably at 30xc2x0 C. to 80xc2x0 C.
The neutralized reaction product preferably has a viscosity between 1000 and 100000 mPas, preferably between 2000 and 80000 mPas (measured at D=10 sxe2x88x921), at room temperature (20 to 25xc2x0 C.).
The dispersing in water is preferably effected by initially introducing the neutralized reaction product comprising polysiloxane containing carboxyl Groups and base and metering in water at 20xc2x0 C. to 90xc2x0 C., preferably at 20xc2x0 C. to 70xc2x0 C., at a rate such that thorough homogeneous mixing is always achieved. It is advantageous to add the water particularly slowly at the beginning. In the course of the metering, the rate of addition can be increased. The viscosity is highest when 30 to 60% of the total amount of the water have been added. In the case of highly viscous polysiloxanes, it is advantageous to add, before the addition of water, a solvent which can be readily removed by distillation after the dispersing. Particularly suitable solvents are tetrahydrofuran, isopropanol, acetone, methyl ethyl ketone, ethanol, cyclohexanol and isobutanol. Acetone and isopropanol and mixtures of acetone and cyclohexanol and mixtures of isopropanol and acetone are particularly preferred.
Suitable polyisocyanates are hexamethylene diisocyanate, isophorone diisocyanate, toluylene diisocyanate, 1-isocyanato-1-methyl-4-isocyanatomethyl-cyclohexane, dimers and trimers of hexamethylene diisocyanate which have uretdione structures or biuret or isocyanurate structures, and bis-1,4-(1-isocyanato-1,1-dimethyl-eth-2-yl)-benzene, bis-1,4-(1-isocyanato-2,2-dimethyleth-2-yl)-benzene, dimeryl diisocyanate and cyclohexylene 1,4-diisocyanate. Hexamethylene diisocyanate, isophorone diisocyanate and n-isocyanato-1-methyl-4-isocyanatomethylcyclohexane are preferred.
Suitable bases for neutralizing the carboxyl groups of the polysiloxane are, for example, sodium hydroxide solution, potassium hydroxide solution, ammonia -and primary, secondary or tertiary amines and alkanolamines. Ammonia, triethylamine, ethanolamine, diethanolamine, methyldiethanolamine, triethanolamine, morpholine, dibutylamine, cyclohexylamine, isopropanolamine, diethylamine, piperidine, N-methylpiperidine and 2,2xe2x80x2,6,6xe2x80x2-tetramethyl-piperidin-4-ol are particularly preferred.
Suitable polycarboxylic anhydrides for the reaction with the hydroxy- and aminopolysiloxanes are maleic anhydride, succinic anhydride, norbornenedicarboxylic anhydride, phthalic anhydride, trimellitic anhydride, cyclohexanedicarboxylic anhydride, cyclohexenedicarboxylic anhydride and pyromellitic dianhydride, preferably maleic anhydride and succinic anhydride. Suitable polydicarboxylic acid derivatives are dimethyl malonate, diethyl malonate, diethyl maleate, dimethyl maleate and monoethyl maleate.
Suitable lactones for the reaction with the aminopolysiloxanes are propiolactone, xcex3-butyrolactone and xcex5-caprolactone, preferably xcex5-caprolactone.
Suitable carbonates for the reaction with the aminopolysiloxanes are ethylene carbonate and propylene carbonate, preferably ethylene carbonate.
Suitable alkylene oxides for the hydroxyalkylation of the aminopolysiloxanes are ethylene oxide, propylene oxide, butylene oxide and epoxycyclohexane, preferably ethylene oxide and propylene oxide.
Preferred aminopolysiloxanes as raw materials for the polysiloxanes according to the invention are those which have 2-aminoethyl-3-aminopropyl substituents or 3-aminopropyl substituents. Aminopolysiloxanes which have pendant functional groups and terminal trimethylsilyl groups are particularly preferred. In general, the substituents are randomly distributed over the main chain of the polysiloxane. Aminopolysiloxanes which carry amino groups at both chain ends and whose chain consists exclusively of dimethylsilyloxy units are furthermore preferred.
Polysiloxanes which contain carboxyl groups and are obtained by complete (100%) or virtually complete ( greater than 95%) reaction of the amino groups of the aminopolysiloxane are furthermore preferred. With nonstoichiometric use of the dicarboxylic anhydrides, in the case of the diamino-functional polysiloxanes and incomplete (e.g. only 50%) reaction of the amino groups, undesired salt formation occurs between amino groups and carboxyl groups after the amide formnation, so that insoluble products or gels may form.
It is also possible to add paraffinic components to the polysiloxane before the emulsification with water and then to effect emulsification. It may be advantageous to use dispersing machines or gap homogenizers and high-pressure nozzles in order to increase the shear force. However, emulsification using a standard stirring unit is preferred since the products can be readily incorporated into water.
It is also possible to disperse the polysiloxane inversely by initially introducing the water and dispersing the neutralized polysiloxane active ingredient at 20 to 100xc2x0 C. in the aqueous phase. However, inverse dispersing is not preferred.
The invention furthermore relates to aqueous dispersions of the polysiloxanes according to the invention. Preferably, these dispersions contain 1 to 60% by weight of polysiloxane and 40 to 99% by weight of water.
The polysiloxane emulsions are preferably characterized by a solids content of 30 to 50% by weight,
a viscosity at 20xc2x0 C. of less than 1000 mPas, preferably less than 500, particularly preferably less than 100 mPas,
a mean particle size of 50 to 700 nm, preferably between 100 and 300 nm, particularly preferably between 100 and 250 nm,
a pH of 6 to 8, preferably 6.5 to 7.5, and
a content of carboxyl groups or of the salts thereof of 0.05 to 1.5 mmol/g of polysiloxane active ingredient.
They can also contain further additives, such as, for example, the paraffins, oils or emulsifiers mentioned below.
Suitable paraffins may be solid or liquid, for example those having a melting point of 10 to 90xc2x0 C., liquid paraffins, mineral oils, white oils, natural oils or fats, such as fish oils, natural or synthetic waxes, such as polyethylene waxes, oxidized polyethylene waxes, polyisobutene waxes, carnauba wax or beeswax.
The amount of the paraffins, oils and waxes in the emulsion may be 0 to 70%, in particular 0 to 40%, based on polysiloxane a).
Suitable emulsifiers are in principle all surface-active compounds having a nonionic, anionic, cationic or amphoteric character which are suitable for emulsification of the polysiloxanes and of the paraffins, oils and waxes and have as little an adverse effect as possible on the imparting of water repellency. Dimethyldodecylamine N-oxide, dimethyltetradecylamine N-oxide and N-(C8-C30)-acylamino acids, such as N-oleylsarcosine, N-laurylsarcocine, N-stearylsarcosine, N-oleylaspartic acid, N-hexadecylaspartic acid, N-stearylaspartic acid or the corresponding derivatives of glutamic acid, fatty acids, such as oleic acid, lauric acid, tallow fatty alcoholates and their ethoxylation products and the sulphuric acid monoesters of the fatty alcohols and of the ethoxylation products of the fatty alcohols are particularly suitable. The acids are present in general in the form of the alkali metal, ammonium, trialkylammonium, or mono-, di- or trialkanolammonium salts. Usually, the polysiloxane emulsions contain 0.0 to 30% by weight, in particular 0.0 to 20% by weight, preferably 0.0 to 5% by weight, of emulsifiers or mixtures of said emulsifiers from the above-mentioned group.
Dispersions of polysiloxanes which contain no additional emulsifier from the above-mentioned group and whose active ingredient in neutralized form has a viscosity of 1000 to 100000 mPas at 20xc2x0 C. and 100 secxe2x88x921, preferably of 2000 to 80000 mPas, are particularly preferred.
The invention furthermore relates to a process for the preparation of the aqueous dispersions, which is characterized in that the polysiloxane according to the invention which contains carboxyl groups and whose COOH groups have been neutralized by bases and are present in the salt formn xe2x80x94COOM is dispersed in water, optionally in the presence of a suitable solvent, and any solvent present is then distilled off.
The dispersing in water is effected in such a way that the neutralized reaction product of polysiloxane containing carboxyl groups and base is initially introduced, preferably dissolved in a solvent, and water is metered in at 20xc2x0 C. to 90xc2x0 C., preferably at 20xc2x0 C. to 70xc2x0 C. at a rate such that thorough homogeneous mixing is always achieved. It is advantageous to add the water particularly slowly at the beginming. In the course of the metering, the rate of addition can be increased. If water is added too rapidly, irreversible deposition of the hydrophobic active ingredient may occur, while excessively slow addition presents no problems. The viscosity is highest on addition of 30 to 60% of the total amount of water. In the case of highly viscous silicone products, it is expedient to add a solvent before the start of the addition of water, which solvent can readily be removed by distillation after dispersing. Particularly suitable solvents are tetrahydrofuran, isopropanol, acetone, methyl ethyl ketone, ethanol, cyclohexanol and isobutanol. Acetone and isopropanol and mixtures of acetone and cyclohexanol are particularly preferred. It is also possible to add paraffinic components, oils or waxes to the polysiloxane before the emulsification with water and then to carry out emulsification. It may be advantageous to use dispersing machines or gap homogenizers and high-pressure nozzles in order to increase the shear force. However, emulsification using a conventional stirring unit is preferred since the products can be readily incorporated into water.
It is also possible to disperse the polysiloxane inversely by initially introducing the water and dispersing the neutralized polysiloxane active ingredient at 20 to 100xc2x0 C. in the aqueous phase. However, inverse dispersing is not preferred.
It is furthermore possible to add to the polysiloxane additives prior to dispersing, in particular the paraffins (component B3) or polyisocyanate adducts (component B4) described below.
In a preferred variant of the water-repellent system,
B1 represents an anionic copolymer prepared by free radical copolymerization of (based in each case on monomer mixture)
xcex1) 10-90 mol % of the ester of a monoethylenically unsaturated C3-C5-carboxylic acid based on an alcohol having 4 to 40 carbon atoms
xcex2) 90-10 mol % of a monoethylenically unsaturated carboxylic acid
xcex3) 0-20 mol % of a monoethylenically unsaturated C4-C6-dicarboxylic anhydride
xcex4) 0-30 mol % of a C2-C8-olefin (isobutene, diusobutylene) and
xcex5) 0-10 mol % of a further comonomer from the group consisting of styrene, alpha-methylstyrene and vinyl esters of C1-C8-carboxylic acids
xe2x80x83and optionally subsequent partial reaction of the anhydride groups with a primary or secondary C1-C40-alcohol and/or a primary or secondary amine having one or two C1-C18-alkyl or alkenyl radicals, with the proviso that at least 20 mol % of the carboxyl groups corresponding to the anhydride groups are not reacted with alcohol and/or amine but are neutralized with a base,
xe2x80x83at least 50 mol % of the carboxyl groups being neutralized. Preferably, the component B1 is present as an aqueous dispersion.
Description of the Component B1 
Suitable copolymers of the component B1 are known per se and are prepared by free radical polymerization in solution or emulsion in the presence of polymerization initiators, optionally emulsifiers, chain transfer agents and customary additives, such as complexing agents.
For example, suitable copolymers are disclosed in U.S. Pat. No. 5,316,860. Polyacrylates prepared by polymerization of a monomer mixture comprising
B1-a) 50-90% of a hydrophobic monomer, such as C12-C30-ester of (meth)acrylic acid, in particular cetyl-eicosyl (meth)acrylate or stearyl methacrylate, and
B1-b) 10-50% of a hydrophilic monomer, such as acrylic acid or methacrylic acid are particularly preferred.
Other suitable copolymer dispersions are disclosed in DE-A 43 34 796. Reaction products of B1-A) terpolymers having an average molar mass Mn of 5000 to 60000, of
B1-c) maleic anhydride,
B1-d) 80-120 mol %, based on component B1-c), of diisobutene and
B1-e) 1-12 mol %, based on component B1-c), of at least one monomer of the formula 
xe2x80x83in which
R31 denotes hydrogen or methyl,
R32 denotes hydrogen, methyl, ethyl, xe2x80x94OR33, 
optionally C1-C4-alkyl-substituted phenyl or hydroxymethyl and R33 denotes C1-C4-alkyl,
with B1-B) aliphatic fatty alcohols having a chain length C6 to C24 and B1-C) subsequent reaction with a base, preferably KOH, NaOH, NH3 or amines,
are particularly preferred.
Terpolymers of maleic anhydride, diisobutene and styrene which have been reacted with C12-C22 fatty alcohols and NaOH are also particularly preferred.
Also suitable are anionic copolymer dispersions prepared by free radical copolymerization of
B1-f) 30-85 mol % of the ester of a monoethylenically unsaturated C3-C5-carboxylic acid based on an alcohol having 4 to 40 carbon atoms
B1-g) 70-15 mol % of a monoethylenically unsaturated carboxylic acid
B1-h) 0-20 mol % of a monoethylenically unsaturated C4xe2x80x94C6-dicarboxylic anhydride
B1-i) 0-30 mol % of a C2-C8-olefin (isobutene, diisobutylene) and
B1-j) 0-10 mol % of a further comonomer from the group consisting of styrene, alpha-methylstyrene and vinyl esters of C1-C8-carboxylic acids
and optionally subsequent partial reaction of the anhydride groups with a primary or secondary C1-C40-alcohol and/or a primary or secondary amine having one or two C1-C18-alkyl or alkenyl radicals, with the proviso that at least 20 mol % of the carboxyl groups corresponding to the anhydride groups are not reacted with alcohol and/or amine but are neutralized with a base, at least 50 mol % of the carboxyl groups being neutralized.
Suitable monomers for the preparation of the components B are: methacrylic acid, acrylic acid, methyl methacrylate, methyl acrylate, butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, octyl methacrylate, octyl acrylate, tallow fatty alcohol methacrylate, tallow fatty alcohol acrylate, stearyl methacrylate, stearyl acrylate, hexadecyl methacrylate, hexadecyl acrylate, dodecylmethacrylate, dodecyl acrylate, eicosanyl methacrylate, eicosanyl acrylate, esters of guerbet alcohols with methacrylic acid or acrylic acid, styrene, alpha-methylstyrene, maleic anhydride, diisobutylene or isobutene, vinyl acetate and vinyl propionate.
Preferred components B1 are amphiphilic copolymers of a hydrophobic monomer from the group consisting of stearyl methacrylate, hexadecyl methacrylate, eicosanyl methacrylate, dodecyl methacrylate, octyl methacrylate and 2-ethylhexyl methacrylate and a hydrophilic monomer from the group consisting of methacrylic acid, acrylic acid, maleic anhydride and optionally further comonomers, such as styrene, diisobutylene or isobutene.
The carboxyl groups in the copolymer may be present in the form of the free acids or as salts. Bases, such as NaOH, KOH, sodium carbonate, ammonia or amines, such as triethylamine, ethanolamine, triethanolamine, diisopropylamine, diethanolamine, N-methyldiethanolamine, octylamine, etc., may be used for the neutralization. 0.5-1.0 equivalent, based on carboxyl groups, of base is preferably used for the neutralization.
Copolymers which are prepared by copolymerizing a monomer mixture comprising
20-90% by weight of a hydrophobic monomer, in particular stearyl methaorylate, hexadecyl methacrylate, eicosanyl methacrylate, dodecyl methacrylate, octyl methacrylate or 2-ethylhexyl methacrylate, and
80-10% by weight of a hydrophilic monomer, in particular methacrylic acid, acrylic acid or maleic anhydride, and
0-30% by weight of a further comonomer from the group consisting of styrene, alpha-methylstyrene and diisobutylene
are particularly preferred.
In a particularly preferred embodiment, polyacrylate dispersions which were prepared by free radical polymerization in the presence of a chain transfer agent and whose carboxyl groups have been neutralized with a base are used, the monomer mixture used consisting of 60 to 85% by weight of stearyl methacrylate or C17.4-methacrylate and 15-40% by weight of acrylic acid. Dispersions which are prepared by dispersion in the presence of the component B3 described below are also preferred. In this embodiment, especially white oil or a liquid C14-C17-liquid paraffin or a wax melting at 30-40xc2x0 C. is particularly preferred as component B3. The amount of component B3, based on the active ingredient comprising B1+B3, is preferably between 30 and 80% by weight, and the amount of solid resin B1 is between 20 and 70% by weight.
Particularly preferred polyacrylate dispersions have an average molar mass of 2000 to 50000 g/mol, preferably 2000 to 20000 g/mol. Such dispersions can be prepared, for example, according to EP 579.267, EP 498 634 and U.S. Pat. No. 5,348,807.
Preferably, the dispersions of component B1 have a solids content of 10 to 60% by weight, preferably 20 to 50% by weight.
Suitable polyacrylate dispersions are known per se. Examples of particularly suitable polyacrylate dispersions are the products of the LUBRITAN(copyright)/LEUKOTAN(copyright) series, in particular Lubritan(copyright) WP, Leukotan(copyright) NS3, Lubritan(copyright) XE/XE 3, Lubritan(copyright) AS and Lubritan(copyright) SP, obtainable from Rohm and Haas.
It has surprisingly been found that the polyacrylates (component B1) in combination with the components B3 impart substantially better hydrophobic character and a better handle to the leather than the polyacrylate dispersions alone if they are used in the water-repellent system together with the polysiloxane a).
The invention therefore also relates to a mixture containing an anionic copolymer and a paraffin, which is used before or together with the polysiloxane a).
A preferred component B2 is a polyaspartic acid derivative having a molecular weight, determined as the number average, of 700 to 30000, preferably 1300 to 16000, obtainable by reacting
B2-A) polysuccinimide having a molecular weight, determined as the number average, of 500 to 10000, preferably 500 to 6000, in particular 1000 to 4000, obtainable by reaction of maleic anhydride and NH3 solution and subsequent condensation, with
B2-B) 5 to 90, preferably 20 to 80, mol %, based on succinimide units of the polysuccinimide, of primary and/or secondary amine whose nitrogen substituents contain 1 to 60, preferably 1 to 36, carbon atoms which may be substituted by hydroxyl radicals and/or interrupted by oxygen atoms, at least 2.5 mol %, preferably at least 15 mol %, in particular at least 30 mol %, of the nitrogen substituents of the amine containing at least 12 carbon atoms, and
B2-C) with 95 to 10 mol %, preferably 80 to 20 mol %, of a ring-opening base in the presence of water.
Suitable components B2 are known per se and are described in DE 195 28 782 and EP 842 300.
Description of Component B2 
The polysuccinimide B2-A) serving as a starting material for the polyaspartamides to be used according to the invention is disclosed in, for example, EP 842 300.
A suitable process starts from maleic anhydride and ammonia, in which the reaction product of maleic anhydride and NH3 is subjected to thermal condensation in the presence of a solvent (cf. EP 842 300). The polysuccinimide formed is then present in solution.
The polysuccinimide serving as a starting compound can also be prepared by thermal dehydration of polyaspartic acid.
In a preferred embodiment, polyaspartic acid derivatives contain repeating aspartic acid units of the following structures 
In general, the amount of the xcex2-form is more than 50%, in particular more than 70%, based on the sum of xcex1-form+xcex2-form.
In addition to these repeating aspartic acid units, further repeating units may be present, e.g.
malic acid units of the formula 
maleic acid units of the formula 
fumaric acid units of the formula 
The xe2x80x9cfurtherxe2x80x9d repeating units may be present in the polyaspartic acid in amounts of up to 100% by weight, based on the sum of xcex1- and xcex2-form of the aspartic acid units.
Preferred polyaspartic acids have molecular weights, determined as the weight average by gel permeation chromatography (calibrated with polystyrene), of 500 to 10000, preferably 1000 to 5000, in particular 2000 to 4000.
The dehydration of polyaspartic acid to polysuccinimide can be carried out at elevated temperature, preferably at 100 to 240xc2x0 C., optionally in the presence of a catalyst, e.g. in the presence of 0.01 to 1% by weight, based on polyaspartic acid, of an acidic catalyst, such as sulphuric acid, phosphoric acid or methanesulphonic acid.
Preferred amines B2-B) for the reaction with the polysuccinimide B2-A) comprise secondary andxe2x80x94preferablyxe2x80x94primary amines, such as, for example, monofunctional polyetheramines having a primary or secondary amino group, such as xcex1-methyl-xcfx89-amino-polyoxyethylene, N,N-dimethylethylenediamine, methylamine, diethylarnine, butylamine, stearylamine, tallow fatty amine, oleylamine, undecylamine, dodecylamine, octylamine, hexylamine, eicosanylarnine, hexadecylamine, 2-ethyl-hexylamine, morpholine, ethanolamine, diethanolamine, bis-2-hydroxy-propylamine, bis-3-hydroxy-propylamine, 2- or 3-hydroxypropylamine, ethoxy-ethylamine, ethoxy-ethoxy-ethylamine, butoxy-ethoxy-ethoxy-ethylamine, 2-methoxy-ethylamine, tetrahydrofurfurylamine, 5-aminopentanol, benzylamine, 4-aminocyclohexylamine, N-methylaminoethyl-sulphonic acid sodium salt, dehydroabietylamine, stearyloxypropylamine, 
The reaction of the polysuccinimide with the amine is disclosed in EP 0 842 300 and is preferably carried out in organic solvents which are inert under reaction conditions. Suitable as such are, for example, lactams, such as caprolactam, N-miethylpyrrolidone and N-methylcaprolactam, polyalkylenediols and their mono- and diethers, such as ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol dimethyl and diethyl ether and diethylene glycol monoethyl ether, and dimethylformamide and dimethyl sulphoxide. The solvent content will not as a rule exceed 30% by weight, based on the total reaction mixture.
The reaction i s carried out in a temperature range from 20 to 160xc2x0 C., the reaction times being between 2 and 72 hours. The product can be isolated by removing the solvent by distillation or by precipitating the product in a nonsolvent, such as acetone, methanol, ethanol, water or isopropanol, and then, if desired, dried.
The polyaspartamides to be used according to the invention can be prepared from the reaction product of B2-A) and B2-B) by opening the remaining incorporated succinimide rings.
Suitable ring-opening bases B2-c) are both alkali metal hydroxides, carbonates and bicarbonates, in particular sodium and potassium hydroxide and sodium carbonate, and ammonia and aminesxe2x80x94including the amines B2-B).
According to a preferred embodiment, maleic acid and maleic anhydride and aqueous ammonia can be mixed in the molar ratio 1:0.75 to 1:1.5 and water distilled off. When the polysuccinimide has reached the desired molecular weight, optionally with concomitant use of an organic solvent, such as diethylene glycol, pyrrolidone, N-methylpyrrolidone, amine B2-B) is metered in and reacted at 130 to 160xc2x0 C. A reaction time of 3 to 18, preferably of 4 to 8, hours is as a rule sufficient for the reaction with amine B2-B). Optionally, an organic solvent may be added. The polyaspartamide which is to be used according to the invention and can be readily dispersed in water with simultaneous opening of the remaining incorporated succinimide rings with ring-opening base B2-c) is formed directly, the concomitant use of customary dispersants being advantageous.
The polyaspartamides to be used according to the invention contain, in an idealized form, repeating structural units of the formulae 
in which
R41, R42 denote hydrogen or one of the radicals designated above as nitrogen substituents, with the proviso that at least one of the two radicals is not hydrogen, and
MB+ represents H+ or an alkali metal ion, an NH4 ion or a primary, secondary or tertiary aliphatic ammonium radical which preferably carries at least one C1-C22-alkyl or C1-C22-hydroxyalkyl group.
Suitable radicals MB+ are, for example, hydroxyethylammonium, dihydroxy-ethylammonium, trishydroxyethylammonium, triethylammonium, ammonium, butyl-ammonium, benzyltrimethylammonium, morpholinium, stearylammonium and oleyl-ammonium.
The structural units I are contained in the polymer preferably in an amount of 5 to 90, in particular 20 to 80, mol %, based on all repeating units. Preferred polyaspartamides contain on average at least one C12-C22-alkyl and/or C12-C22-alkylene radical per structural unit I.
The structural units II are contained in the polymer preferably in an amount of 95 to 10, in particular 80 to 20, mol %, based on all repeating units. Polyaspartamides whose carboxyl groups are present in partly neutralized form are particularly preferred. The preferred degree of neutralization is 10 to 80, preferably 20 to 60%.
The structural units III are contained in the polymer in an amount of 0 to 5 mol %, based on all repeating units. Preferred polyaspartamides contain less than 1 mol % of the structural units III.
Preferred nitrogen substituents R41, R42, independently of one another, comprise, for example, optionally hydroxyl-substituted C1-C22-alkyl or C2-C22-alkenyl groups, such as hydroxyethyl, hydroxypropyl, methyl, ethyl, butyl, hexyl, octyl, octenyl, decyl, undecyl, undecenyl, dodecyl, tetradecyl, hexadecyl, oleyl, octadecyl or 12-hydroxy-octadecenyl, C5-C10-cycloalkyl radicals, such as cyclohexyl, C12-C30-radicals interrupted by oxygen atoms, such as stearoyloxyethyl or stearyloxyethoxyethyl, and are derived from the above-mentioned amines B2-B).
Nitrogen substituents interrupted by oxygen atoms are best introduced by using corresponding aminoethers.
The polyaspartamides to be used according to the invention are self-dispersing, particularly if the amount of structural units I is less than 50 mol %. However, external dispersants may also be concomitantly used.
Preferred dispersants comprise, for example, C8-C18-n-alkylsulphates, C8-C18-n-alkyl-benzenesulphonates, C8-C18-n-alkyl-trimethyl-ammonium salts, n-di-C8-C18-alkyl-dimethyl-ammonium salts, C8-C18-n-alkyl-carboxylates, C8-C18-n-alkyldimethylamine oxides andxe2x80x94preferablyxe2x80x94oligoethylene glycol mono-C6-C18-alkyl ethers having on average 2 to 30 ethoxy groups per molecule. The n-alkyl radicals may also be replaced by partially unsaturated linear aliphatic radicals. Particularly preferred dispersants are oligoethylene glycol mono-C10-C14-alkyl ethers having on average 4 to 12 ethoxy groups per molecule, in particular oligoethylene glycol mono-C12-alkyl ethers having on average 8 ethoxy groups per molecule.
Preferred dispersants furthermore comprise oleic acid, oleic acid sarcosides, ricinoleic acid, stearic acid, fatty acid partial esters of polyols, such as glycerol, trimethylolpropane and pentaerythritol, and their acylation, ethoxylation and propoxylation products, e.g. glyceryl monostearate and monooleate, sorbitan monostearate and monooleate, sorbitan tristearate and trioleate and their reaction products with dicarboxylic anhydrides, such as succinic anhydride, maleic anhydride, phthalic anhydride or tetrahydrophthalic anhydride, reaction products of bis-(hydroxymethyl)-tricyclodecane and maleic anhydride or succinic anhydride and their derivatives, preferably in the form of their alkali metal or ammonium salts.
Particularly preferred dispersants are salts of long-chain fatty acids, preferably oleic acid and an amino alcohol, preferably hydroxyethylamine, bishydroxyethylamine or trishydroxyethylamine.
The dispersion of the polyaspartamides to be used according to the invention can be formed by dispersing the polyaspartamides in an aqueous dispersant solution, preferably with heating to temperatures of 40 to 95xc2x0 C., with stirring.
In general, it is advisable to disperse the polyaspartamides to be used according to the invention without intermediate isolation, directly from the reaction mixture, which optionally contains organic solvent. Thus, for example, the dispersant can be added to the reaction mixture and an aqueous solution of the ring-opening base B2-c) can be metered in while stirring at temperatures of 70 to 130xc2x0 C., so that a mixing temperature of 70 to 95xc2x0 C. is established, and optionally the organic solvent can be distilled off. Conversely, it is of course also possible to disperse the reaction mixture inversely in aqueous dispersant solution or a mixture of reaction mixture and dispersant in water. It is also possible to dispense with the removal of the solvent.
The use of ring-opening bases B2-c) for establishing the pH after dispersing is also preferred. pH values of 5.5 to 11, especially of 6.0 to 9, are particularly preferred. It is also preferable to subject the dispersion to bleaching with oxidizing agents. Hydrogen peroxide, ammonium persulphate or sodium sulphate is particularly suitable. After the end of the bleaching, unconsumed oxidizing agent is deactivated with a reducing agent or by enzymatic decomposition. Suitable reducing agents are sodium bisulphite, sodium dithionite and the corresponding potassium and lithium salts or an enzymatic reducing agent (BAYREDUKT(copyright) EPK).
The dispersant content is in general not more than 30, preferably 3 to 15, % by weight, based on the prepared dispersion.
The solids content of the dispersionsis 5 to 70% by weight, preferably 20 to 50% by weight. The mean particle size of the dispersed polyaspartamides is in general 50 to 1000, preferably 50 to 700 and in particular 50 to 400 nm.
Particularly in the case of solids contents above 45% by weight, the dispersions may be present in the form of pastes, which however can readily be diluted with water. Preferred dispersions having a solids content of 30-40% by weight are present as a rule as low-viscosity emulsions which have a viscosity of  less than 1000 mPas at 20xc2x0 C. The pH of the dispersions is between 5 and 10, preferably in the pH range between 5 and 9.
A particularly preferred component B2 is obtainable by
B2-a) reacting maleic anhydride, optionally in an inert solvent, with ammonia in the molar ratio 1:1.0 to 1:1.3 and effecting thermal condensation, the water formed being distilled off,
B2-b) reacting the product from B2-a) with at least one amine of the formula 
in which R41 and R42 have the stated meaning, 0.2 to 0.5 mol of amine (I) being used per 1 mol of maleic anhydride, and
B2-c) dispersing the reaction product, optionally in the presence of a dispersant, in an aqueous phase which contains a base, and adjusting the product in solids content, viscosity, pH, particle size and colour, depending on the intended use, and optionally subjecting it to bleaching.
A preferred component B3 is a paraffinic hydrocarbon which optionally may be substituted by hydroxyl and/or carboxyl groups (white oil 285, liquid paraffin, paraffin wax, montan wax, carnauba wax, oxidized polyethylene, long-chain fatty alcohols, such as guerbet alcohols, fatty acids, fatty acid esters, phospholipids), the paraffinic hydrocarbon preferably giving a stable dispersion together with the component B1 and/or B2.
Description of the Component B3 
Suitable components B3 are, for example, paraffinic hydrocarbons, such as C10-C60-paraffins, in particular C14-C17-liquid paraffins, white oil, waxes, fatty alcohols, such as stearyl alcohol, oleyl alcohol or mixtures thereof, such as tallow fatty alcohol, and moreover commercial wool wax alcohol, commercial carnauba wax, commercial polyethylene wax, montan wax, guerbet alcohols and reaction products of the fatty alcohols with dicarboxylic anhydrides, preferably maleic anhydride and succinic anhydride, fatty acids, such as commercial dimeric fatty acids, it being possible for the carboxyl groups contained in the waxes to be present in free form or in neutralized form as salts. C14-C17-Liquid paraffins, white oil and waxes having a softening point between 25 and 60xc2x0 C. are particularly preferred.
Bases, such as NaOH, KOH, sodium carbonate, ammonia or primary, secondary or tertiary amines or amino alcohols, are suitable for the neutralization. KOH, NaOH, ammonia, ethanolamine, morpholine, diethanolamine, triethylamine and triethanolamine are particularly preferred.
The components B3 are preferably present as aqueous dispersions. The solids content of such dispersions is 5 to 60% by weight, preferably 10 to 35% by weight.
It is furthermore particularly preferable to use the component B3 together with components B1 and B2. For this purpose, the component B3 is preferably added to component B1 and/or B2 and converted into a stable dispersion by using high shear forces with the aid of customary dispersing machines, dissolvers, homogenizers or ultrasonic apparatuses.
Preferably, such dispersions have the following composition:
1 to 50% by weight of component B1 (calculated in each case as solids content) and/or component B2,
0 to 50% by weight of component B3 (calculated in each case as solids content),
0 to 99% by weight of water (total=100%).
Mixtures of components B3 and B1 are particularly preferred.
Particularly preferred mixtures of component B1 and component B3 are those which have the following composition:
3 to 30% by weight (based on solids content) of B1,
10 to 40% by weight (based on solids content) of B3,
30 to 87% by weight of water (total=100%).
Mixtures of component B1 and component B3 having a solids content of 10 to 70% by weight, preferably 20 to 50% by weight, are very particularly preferred.
It is also preferable that the component B3 as such is added to a component B1 and/or B2, prior dispersing of the component B2 in water not being required.
A preferred component B4 is a reaction product of
B4-a) an organic polyisocyanate
B4-b) 0.0 to 0.9 equivalent of C6-C24-alcohol, preferably C12-C18-alcohol, per equivalent of NCO or latent NCO contained in B4-a),
B4-c) 0.1 to 1.0 mol of cyanamide per equivalent of NCO or latent NCO contained in B4-a) and
B4-d) ammonia or volatile amine as neutralizing agent for the cyanamide groups, the reaction products being free of polyester or polyether groups and free of halogen atoms.
The term xe2x80x9ccyanamide groupsxe2x80x9d in the context of the invention comprises functional groups of any type, provided that they contain groups of the formula 
i.e. for example, cyanourea groups 
or cyanoaminocarbonylurea groups 
and groups containing the salts of these compounds and of the formula 
Preferred isocyanate adducts (component B4) are also the anionically modified polyureas which are described in DE-A 41 33 572 and EP-A 0 538 649 and in EP-A 0 814 102 (Examples 1-3) and which are based on
I. a) organic polyisocyanates and
II. polyfunctional NCO-reactive compounds from the series comprising
b) polyhydroxy compounds,
c) polyamines,
d) amino alcohols and optionally
III. monofunctional NCO-reactive compounds e) and optionally
IV. water f),
which contain anionic N-cyanoaminocarbonylurea groups of the formula 
incorporated into the polymer chain and optionally terminal anionic cyanourea groups of the formula 
wherein the ratio of groups incorporated into the polymer chain to terminal groups is higher than 1:1 and wherein [cation]⊕ represents an alkali metal ion or an optionally substituted ammonium ion.
Preferred isocyanate adducts (component B4) which are described in EP-A 0 814 102 are also the graft copolymers of unsaturated monomers on cyanamide groups containing, anionically modified polyurethane urea dispersions as the graft substrate, which are in turn obtainable by the reaction of NCO prepolymers with cyanamide.
When component B4 is used as an emulsifier, very soft leathers having outstanding handle are formed.
A substantial advantage of component B4 is that it reacts in the leather to give a water-insoluble (nonhydrophilic) dimer or oligomer and consequently is neither washed out nor migrates significantly as soon as this reaction is complete and loses its emulsifying effect.
Description of Component B4 
Component B4 is disclosed for example in DE-A 41 33 572 or EP 0 814 102 and is preferably obtained by reacting a polyurea containing oxadiazinetrione structures of the formula (ii) 
and/or uretdione units of the formula (i) 
with a cyanamide salt of the formula Hxe2x80x94NExe2x8ax96xe2x80x94CN [cation]⊕, wherein [cation]⊕ represents an alkali metal ion or an optionally substituted ammonium ion. Particularly preferred anionically modified polyureas are for example the polyureas according to Examples 1 to 5 of DE-A 41 33 572 and according to Examples 1 to 3 of EP-A 0 814 102.
The component B4 is disclosed, for example, in DE 43 30 378 and is preferably prepared by reaction of NCO groups in polyisocyanates with a C6-C24-alcohol and then with cyanamide and subsequent neutralization with ammonia or volatile bases. The reaction products no longer contain free NCO groups and are soluble in water or emulsifiable in water. The reaction with the C6-C24-alcohol can, if required, also be omitted.
The anionic polyisocyanate adducts preferably have average molar masses (number average) of less than 5000 g/mol, preferably of 300 to 3000 g/mol.
Suitable polyisocyanates are in particular aliphatic polyisocyanates having at least 2 free isocyanate groups per molecule. Diisocyanates T(NCO)2 are preferably used, T representing a divalent aliphatic hydrocarbon radical having 4 to 12 carbon atoms or a cycloaliphatic or aromatic radical having 6 to 15 carbon atoms or an araliphatic radical having 7 to 15 carbon atoms. The following may be mentioned by way of example: butylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diisocyanato-cyclohexane, 4-isocyanato-4-methyl-1-isocyanatomethyl-cyclohexane, bis-cyclohexylmethane 4,4xe2x80x2-diisocyanate (H12 MDI), nonyl triisocyanate, 1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene (2,4-TDI), 2,6-diisocyanatotoluene (2,6-TDI), p-xylylene diisocyanate, 4,4xe2x80x2-, 2,2xe2x80x2- and 2,4xe2x80x2-diisocyanato-diphenylmethane (MDI) and mixtures thereof.
The customary polyisocyanates which are known per se in polyurethane chemistry, have a higher functionality and are obtainable, for example, by trimerization of hexamethylene diisocyanate or isophorone diisocyanate or mixtures thereof and which contain isocyanurate units as additional structural units and may have an NCO functionality of 2 to 3.5 are also preferably used. Such trimers are commercially available (BAYER AG, products of the DESMODUR(copyright) series).
Commercially available modified polyisocyanates which are known per se, are obtained by catalytic dimerization of hexamethylene diisocyanate and contain additional uretdione structural units (i) 
and optionally also isocyanurate structures are also suitable. Polyisocyanates which contain oxadiazinetrione structural units (ii) 
and which are derived from hexamethylene duisocyanate are also suitable. Modified polyisocyanates which are known per se, contain carboduimide, urea, urethane, allophanate or biuret groups and may also have an NCO functionality between 2.0 and 3.5 and are derived from hexamethylene diisocyanate are furthermore suitable.
Particularly preferred HDI polyisocyanates containing biuret groups are those which have an NCO fuinctionality of 2.5 to 3.5, for example DESMODUR(copyright) N 3200 (Bayer AG).
The polyisocyanates described above can also be used as a mixture.
Diisocyanates in turn, of the formulae (iii) and/or (iv) 
in which the radicals
R51, independently of one another, represent the divalent radical of an aliphatic hydrocarbon having 1 to 15 carbon atoms, of a cycloaliphatic hydrocarbon having 3 to 15 carbon atoms, of an araliphatic hydrocarbon having 7 to 15 carbon atoms or of an aromatic hydrocarbon having 6 to 12 carbon atoms,
are suitable as components for introducing oxadiazinetrione and/or uretdione structural units of the formulae (i) and (ii), respectively.
Examples of such polyisocyanates B4-a) are 1,3-bis-(5-isocyanato-1,3,3-trimethylcyclohexyl-methylene)-2,4-dioxo-1,3-diazetidine; 1,3-bis-(3-isocyanato-4-methylphenyl)-2,4-dioxo-1,3-diazetidine; 1,3-bis-(6-isocyanato-hexyl)-2,4-dioxo-1,3-diazetidine; 3,5-bis-(5-isocyanato-1,3,3-trimethyl-cyclohexyl-methylene)-2,4,6-trioxo-tetrahydro-1,3,5-oxadiazine; 3,5-bis-(4-isocyanato-cyclohexyl)-2,4,6-trioxo-tetrahydro-1,3,5-oxadiazine and 3,5-Bis-(6-isocyanato-hexyl)-2,4,6-trioxo-tetrahydro-1,3,5-oxadiazine (Desmodur(copyright) LB 202, Bayer AG).
Among the isocyanates of the formulae (iii) and (iv), those of the oxadiazinetrione series (iii) are preferably used, particularly preferably 3,5-bis-(6-isocyanatohexyl)-2,4,6-trioxo-tetrahydro-1,3,5-oxadiazine.
Since isocyanate groups are lost as a result of reaction with the alcohol B4-b), polyisocyanates having more than 2 isocyanate groups are very particularly preferred. These isocyanates include isocyanurates, biurets, trisurethanes (and their analogues having a higher functionality) of TDI, IPDI, MDI, HDI and H12-MDI, of 1,4-diisocyanatocyclohexane, etc. Owing to the better lightfastnesses, here too the aliphatic polyisocyanates are very particularly preferred.
Examples of suitable polyisocyanates are trimers of hexamethylene diisocyanate, 1,3-bis-(6-isocyanatohexyl)-2,4-dioxo-1,3-diazetidine, 3,5-bis-(6-isocyanatohexyl)-2,4,6-trioxo-tetrahydro-1,3,5-oxadiazine (DESMODUR(copyright) LB 202). If the reaction with a C6-C24-alcohol is carried out, the polyisocyanates having a functionality greater than 2 are preferred because a part of the NCO functionality is lost as a result of the reaction with the alcohol.
Suitable C6-C24-alcohols are alkanols, such as n-hexanol, n-octanol, 2-ethylhexanol, dodecanol, cetyl alcohol, stearyl alcohol, hydrogenated tallow fatty alcohols or guerbet alcohols, or alkenols, such as oleyl alcohol, tallow fatty alcohol, cyclohexenol, butenol, hexenol, hexadecenol or octadecenol.
Suitable bases for neutralizing the cyanamide groups B4-d) are ammonia and volatile amines, preferably tertiary amines having up to 12 carbon atoms, such as triethylamine, trimethylamine, triisopropylamine, tri-n-butylamine, N,N-dimethylaminoethanol, N-methylmorpholine, pyridine and triisopropanolamine. Ammonia and triethylamine are particularly preferred.
The component B4 is prepared by reacting a polyisocyanate B4-a), optionally partially, with a C6-C24-fatty alcohol B4-b) and reacting the modified polyisocyanate or the unmodified polyisocyanate in water in the presence of cyanamide B4-c) and neutralizing agent (base) B4-d), or in the presence of a cyanamide neutralized with a base, to give the desired end product.
The reaction temperature is in general between 20 and 100xc2x0 C., preferably between 30 and 60xc2x0 C. The reaction is complete when the end product no longer has any free NCO groups. In a preferred embodiment 0 to 0.7 mol, particularly preferably 0 to 0.3 mol, of alcohol B4-a) per NCO equivalent of polyisocyanate B4-b) is used. The remaining NCO groups are then further reacted with cyanamide B4-c) and neutralizing agent B4-d). It is possible to use cyanamide and neutralizing agent in excess. In this case, the other NCO groups react with the alcohol or water.
Dispersions or solutions B4 are obtained, depending on the presence or type and/or proportion of the fatty alcohol component. The solids content of this solution or dispersion is preferably 5 to 70% by weight, particularly preferably 20 to 60% by weight. The remainder is water.
A reaction product of a hexamethylene diisocyanate trimer containing biuret groups (Desmodur(copyright)3200) or of a hexamethylene diisocyanate trimer containing isocyanurate groups (Desmodur(copyright) N 3300, N 3600) and 1 mol of cyanamide per equivalent of NCO and 1 mol of triethylamine per equivalent of cyanamide is particularly preferred. The product is dispersed in water, a 40-60, in particular 50-60, % strength solution being obtained.
The component B4 is preferably present as an aqueous dispersion or solution.
The component B4 has the following properties:
on drying and giving up its opposite ion, the compounds dimerize or oligomerize and lose their ionic character;
they thus also lose their dispersing properties; polymers dispersed therewith are precipitated;
if they have radicals of relatively long-chain alcohols B4-b), they can support in particular hydrophobic properties;
if the products B4 have a functionality greater than 2, they act as crosslinking agents.
They are particularly suitable for:
retanning of leather with softening and optionally imparting of hydrophobic properties;
reinforcing the water-repellency effect when components B1) to B4) and polysiloxanes a) are used;
use as a dispersion stabilizer for other customary leather auxiliaries;
use as an emulsifier for silicones.
If the components B4 are used as emulsifiers for component a) (polysiloxane containing carboxyl groups), they can be used in amounts of 0.1 to 100% by weight (solid reaction product), based on the amount of the polysiloxane active ingredient. The use of 0.1 to 50, preferably 0.1 to 10, % by weight (solid reaction product), based on the amount of the polysiloxane active ingredient, is in general sufficient.
The mixtures to which the components B4 have been added can be converted into a dispersion in a simple manner (by stirring or pouring into the liquor used). Component B4 is generally poured into the retanning liquor or the water-repellent liquor which contains the component a); the dispersion is taken up as a result of the rotary movement of the drum or of the tanning machines. The pH of the retanning liquor or of the leather should be above 4, preferably above 5 to 5.5. Of course, synthetic tanning agents, polymer tanning agents and mineral tanning agents, fatliquoring agents and dyes can also be added. By adding acid, the component B4 can be selectively dimerized or oligomerized.
It is also particularly preferable to use the component B4 as a self-inhibiting emulsifier mixed with component a) and/or mixed with the components B1 to B3 or mixtures thereof.
It is very particularly preferable to use component B4 in combination with component a). Preferably, these mixtures have the following composition:
The preparation of such mixtures is carried out, for example, by dissolving a dispersion or solution of the component B4 in an emulsion of the component a) at 10 to 60xc2x0 C. It is also possible to dissolve or to disperse the active ingredient of component B4 in the polysiloxane and to disperse the resulting mixture together in water, as has already been described for the preparation of the polysiloxane emulsion (component a).
Water-repellent systems containing (based on the system)
1) 1 to 60% by weight of a dispersion consisting of (calculated in each case as solids content)
and
2) 0.1 to 40% of a polysiloxane emulsion comprising (calculated in each case as solids content)
and water to make up to 100% are preferred.
Water-repellent systems containing
1) 1 to 60% of a dispersion consisting of
1.1) 3 to 30% of component B1 (calculated in each case as solids content)
1.2) 10 to 40% of component B3 (calculated in each case as solids content)
1.3) 30 to 87% of water
and
2) 0.1 to 40% of a polysiloxane emulsion comprising
and water to make up to 100% are particularly preferred.
It has furthermore been found that the leathers which are produced by use of the components B1 and B3, and B2 and B3, and a subsequent top water-repellent treatment with polysiloxanes a), optionally with addition of the component B4, give a particularly good result and best fulfil the spectrum of the objects set in its totality.
The invention also relates to a process for imparting water repellency to substrates, preferably those having a flexible, in particular fibrous structure, which is characterized in that the substrate is treated with the polysiloxane according to the invention and/or with the water-repellent system according to the invention, in particular with the water-repellent system according to the invention.
Suitable substrates may be: cellulose-containing materials, such as paper, board, cardboard, nonwovens, textile structures such as wool or cotton articles, leather, hides and leather substitution products, preferably leather and hides.
The retanning of the substrates with softening and/or imparting of water repellency to the substrates is preferably carried out by treating the substrates with an aqueous liquor which contains the polysiloxane according to the invention and/or the water-repellent system according to the invention. For this purpose, the substrate is brought into contact with the liquor by application by means of rollers or in a container, in the case of leather preferably in a tanning drum. After the treatment, the substrate is dried.
The retanning of leather, hides and leather fibre material with softening and/or imparting of water repellency to leather, hides and leather fibre material consists of several individual steps, wet blue, i.e. chrome-tanned skins and hides, preferably being used as starting material. The process steps are to be explained in detail for wet blue:
1. Neutralization of the chrome-tanned leather
2. Retanning and optionally dyeing
3. Addition of the polysiloxane according to the invention, in particular in the form of the water-repellent system (metering of the components a) and b) either together or preferably in succession).
In a preferred embodiment, one or more components from the group B1, B2, B3 or B4 are metered independently of one another in process step 3 and, after an action time of 0.1 to 5 hours, the component a), optionally in combination with component B4, is added. After a further 0.1 to 5 hours, the procedure is continued with process step 4.
After step 3, fixing is optionally effected with metal salts or with Cr(III) salts, but compulsorily and preferably fixation with formic acid or with an inorganic acid is carried out. This is preferably effected by the process steps 4 to 6.
4. Reduction of the pH by addition of a carboxylic acid, preferably formic acid, to pH less than 4.5, preferably to 3.0 to 4.5
5. Washing
6. Customary finishing (setting-out or samming, drying by hanging, staking, application of a vacuum (1 minute, 70xc2x0 C.)).
In an embodiment which is likewise preferred, component B1 or B2 or a mixture of components B1 and B3 or a mixture of components B2 and B3 is metered after process step 2 and, after an action time of 0.1 to 5 hours, the component a) or a mixture of components a) and B4 is added. After a further action time of 0.1 to 5 hours, the procedure is continued with process step 4.
Advantages of the process according to the invention are:
1. No chromium salts or other mineral salts are required for fixing.
2. Additional fatliquoring agents can be used for establishing a soft handle but are not necessary.
3. The application can also be carried out in a so-called compact procedure:
Here, preferably the components B1+B2 or B1+B3 or B2 +B3 or B1+B2+B3 of b) of the water-repellent system are added, for example as a mixture, after the neutralization of the leather and, after a specific run time, preferably after 1 to 5 hours at 20-60xc2x0 C., the component a) and optionally the component B4 as a mixture with a) are added without discharging the liquor or a wash process. After a run time of a) or B4+a) of about 1 to 2 hours at 20-60xc2x0 C., the formic acid is added to the same liquor and the products a) and b) are fixed. As a result of this procedure and the good liquor exhaustion, hardly any wastewaters are obtained.
4. For fixing the polysiloxane/dispersions according to the invention, it is sufficient to reduce the pH by adding a carboxylic acid having a pKa value of less than 5 after a sufficient run time with the water-repellent system. The liquor exhaustion is as a rule so good that addition of the acid in the drum is possible even without discharging the liquor for imparting water repellency. Preferred pH values should be less than 4.5, in order to achieve sufficient fixing in the hide substance. The range between 3.0 and 4.5 is particularly preferred. A preferred carboxylic acid is formic acid. It is also possible to use an inorganic acid, in which case it should be ensured that the pH is adjusted to between 3.0 and 4.5. The run time with the acid is as a rule 0.1 to 5 hours.
Instead of fixing with a carboxylic acid or in combination with an acid fixing, it is also possible to add polyvalent metal compounds, such as aluminium, titanium, zirconium or chromium salts or carboxylates or alkoxides, to the liquor. For ecological reasons, however, this is generally dispensed with. At least fixing with a mineral salt has no advantage over fixing with acid.
To achieve a sufficient water-repellent effect. the following amounts (data in solids content, based on shaved weight of leather or wet weight of the hides) are preferably used in the process according to the invention:
0 to 30% by weight of component B1, preferably 0.1 to 15% by weight of B1,
0 to 30% by weight of component B2, preferably 0.1 to 15% by weight of B2,
0 to 50% by weight of component B3, preferably 0.1 to 20% by weight of B3,
0 to 20% by weight of component B4, preferably 0.1 to 5% by weight of B4,
0.1 to 25% by weight of component a), preferably 0.1 to 6% by weight of a),
the amounts being used independently of one another and the amounts of the components B1 to B4 used preferably not simultaneously being 0% by weight.
The pH of the liquor is preferably 5.5 to 7 at the beginning of the procedure for imparting water repellency. The pH can optionally be corrected before the addition of the water-repellent system by adding bases such as ammonia or sodium bicarbonate. To achieve a sufficient water-repellent effect, in particular up to 10% by weight, preferably up to 8% by weight, of active substance of the polysiloxane a) according to the invention, based on shaved weight or skin weight, are used according to the process according to the invention. The treatment is effected at a temperature between 20 and 60xc2x0 C., preferably between 35 and 50xc2x0 C. After the treatment, the liquor has a pH of about 5 to 6. By adding a carboxylic acid, the pH is reduced to 3 to 4.5. A preferred carboxylic acid for the acidification is formic acid. The acidification preferably takes place for up to half an hour at 20-60xc2x0 C. Thereafter, the leather is thoroughly washed with water and is finished in the customary manner.
In a particularly preferred embodiment, the process for the production of water-repellent leathers is carried out as follows (the stated amounts are relative to active substance or solids content, based on shaved weight of the leather or wet weight of the hides):
1. Neutralization
Wet blue is first neutralized with a liquor containing 1% of sodium bicarbonate and 1% of sodium formate, at 20-60xc2x0 C. (run time 2 to 24 hours) so that a pH between 5.0 and 5.5 results. Liquor length 100 to 400%. The leather is then rinsed.
2. Retanning/Dyeing
A fresh liquor containing a retanning agent, e.g. a vegetable tanning agent, such as chestnut bark extract (sweetened chestnut) and a synthetic tanning agent (such as TANIGAN QF), and a dye (for example BAYGENAL Brown CGG) is added. The drum is allowed to run for from 1 to 5 hours at 20-60xc2x0 C., preferably at 30-45xc2x0 C. Finally, the liquor is discharged and washing is effected.
3. Imparting Water Repellency
A liquor which contains 0.1-0.5% of ammonia of 0.3-0.5% of NaHCO3 is introduced into the tanning drum and further neutralization is effected for 10-60 minutes, after which the liquor is discharged. 2-8% by weight of the component B1) and/or B2), or 2 to 8% by weight of a prepared formulation comprising B1) and/or component B2) containing component B3), and 100% of water are then added (liquor length 50-200%). After a drumming time of 1-3 hours at 20-60xc2x0 C. and complete exhaustion of the liquor, 0.5-2.5% of the component a) or of a mixture a)+B4 are added without further addition of water and drumming is carried out for a further 30-120 minutes at 20-60xc2x0 C.
4. Fixing
0.3-2% of formic acid (85% strength, 1:10) are then added without liquor change, and the leather is acidified to pH 3.0-4.5, preferably to pH 3.5-4.0. The liquor is then discharged.
5. Finishing
First washing with warm water (30-50xc2x0 C.), setting-out or samming is effected and the leather is finished in a customary manner (hanging to dry, staking, application of a vacuum for 1 minute at 50-70xc2x0 C.).
The process according to the invention gives leather having outstanding hydrophobic properties and a soft and full handle.